The present invention relates generally to methods and apparatus for producing waveforms of musical tones, voices or other desired sounds on the basis of waveform data read out from a waveform memory or the like, and more particularly to an improved waveform production method and apparatus capable of producing waveforms that are faithfully representative of color (timbre) variations effected by various styles of rendition or articulation peculiar to natural musical instruments. Note that the present invention is applicable extensively to all fields of equipment, apparatus or methods capable of producing waveforms of musical tones, voices or other desired sounds, such as automatic performance apparatus, computers, electronic game apparatus or other types of multimedia equipment, not to mention ordinary electronic musical instruments. It should also be appreciated that in this specification, the term “tone” is used to refer to not only a musical tone but also a voice or other sound, and similarly the terms “tone waveform” are used to embrace a waveform of a voice or any other desired sound, rather than to refer to a waveform of a musical tone alone.
The so-called “waveform memory readout” method has been well known, in which waveform data (i.e., waveform sample data), encoded by a desired encoding technique, such as the PCM (Pulse Code Modulation), DPCM (Differential PCM) or ADPCM (Adaptive Differential PCM), are prestored in a waveform memory so that a tone waveform can be produced by reading out the waveform data from the memory at a rate corresponding to a desired tone pitch. There have been known various types of waveform memory readout techniques. Most of the known waveform memory readout techniques are intended to produce a waveform from the beginning to end of a tone to be generated. Among examples of the known waveform memory readout techniques is one that prestores waveform data of an entire waveform from the beginning to end of a tone to be generated, and one that prestores waveform data of a full waveform section for an attack portion or the like of a tone having complicated variations but prestores predetermined loop waveform segments for a sustain or other portion having little variations. In this specification, the terms “loop waveform” are used to refer to a waveform to be read out in a repeated (looped) fashion.
In these waveform memory readout techniques prestoring waveform data of an entire waveform from the beginning to end of a tone to be generated or waveform data of a full waveform section for an attack portion or the like of a tone, there must be prestored a multiplicity of various waveform data corresponding to a variety of rendition styles (or articulation) and thus a great storage capacity is required for storing the multiplicity of waveform data.
Further, although the above-mentioned technique designed to prestore waveform data of an entire waveform can faithfully express color (timbre) variations effected by various rendition styles or articulation peculiar to a natural musical instrument, it can only reproduce tones just in the same manner as represented by the prestored data, and thus it tends to encounter poor controllability and editability. For example, it has been very difficult for the technique to perform control of waveform characteristics, such as time axis control, according to performance data, of the waveform date corresponding to a desired rendition style or articulation.
To address the above-discussed inconveniences, more sophisticated techniques for facilitating realistic reproduction and control of various rendition styles (or articulation) peculiar to natural musical instruments have been proposed in Japanese Patent Laid-open Publication No. 2000-122665 and the like; these techniques are also known as SAEM (Sound Articulation Element Modeling) techniques. In the case of such SAEM techniques, when a plurality of rendition style waveform modules are to be time-serially connected together to create a continuous tone waveform, it is desired to connect the rendition style waveform modules without unnaturalness.